| 摘要 |
A power-up/power-down safety switch includes a simple, low-cost circuit having one AND gate, which may be a CMOS IC, one voltage-limiting diode and three resistors. The circuit functions in conjunction with a logic control circuit in a manner which assures that the inhibiting voltage to the logic control circuit VINH is equal to (or slightly less than) the supply voltage, VCC(t), until VCC(t) reaches the minimum required supply voltage for the circuit logic to operate properly. VINH is then rapidly switched to a low state such that the circuit logic operates without interference. Conversely, when the circuit is turned OFF, the value of VINH is switched to a high state as soon as the supply voltage reaches the minimum value to operate the logic circuit thereby again causing the logic outputs to go low and that all the drive signals to the power switch are in the OFF state.
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